Simple drawing over image?

[Andrei]

I'm trying to do the following in Julia: 

1. read image

2. draw some basic graphics (like lines and circles) over it 

3. display it

Points (2) and (3) may go the other way, i.e. I don't really care if drawing is done on image array in memory or on canvas. 

However, I'm not sure what's the easiest way to implement this logic. Basically, I'm using Images.jl and ImageView.jl, but it seems like they don't support drawing at all (except for modifying underlying arrays, of course). On other hand, there's Cairo and Tk, which are powerful, but seem to be terrible overkill for such a simple task. 

So I'm wondering: 

1. is there an easy way to do "just this"? 

2. If not, what is the minimal set of packages/actions needed to implement this logic? 

[Tim Holy]

ImageView has an annotation framework; it's documented in the README.

--Tim

[Andrei Zh]

Ah, my fault. I should have checked it before googling more sophisticated things. Thanks! 

[Max Suster]

You can do this easily in OpenCV.jl.  An example of drawing is already in the README.md. 

[Cristóvão Duarte Sousa]

I usually draw with Compose.jl and then overlay the draw to an Images.jl image with a function I'd made:

using Images, TestImages, Compose, Color
import Compose.compose

function compose(img::Image, c::Context)
    width, height = size(img)
   
    surface = Cairo.CairoARGBSurface(zeros(Uint32, height, width))
    draw(PNG(surface), c)
    overlay = reinterpret(BGRA{FixedPointNumbers.Ufixed8}, surface.data)
   
    outimg = similar(img)
    for i=1:width, j=1:height
        alpha = overlay[i,j].alpha
        overlay_pixel = convert(eltype(img), overlay[i,j])
        beta = one(alpha) - alpha
        outimg[i,j] = beta*img[i,j] + alpha*overlay_pixel
    end
   
    outimg
end

For example,

testimg = testimage("lighthouse")


width,height = size(testimg)


c = compose(context(),  line([(1,1), (width,height)]))
c = compose(c,  line([(width,1), (width/2,height/2)]))
c = compose(c, stroke(color("yellow")))


c = compose(context(units=UnitBox(0, 0, width, height)), c)


compose(testimg, c)

Regards,

Cristóvão

[Max Suster]

To be more precise, in OpenCV.jl, you can do the following:

1. read image

filename = "your image"

img = imread(filename)

2. draw some basic graphics (like lines and circles) over it

center = cvPoint(260,275)
radius = 30
color = cvScalar(0,0,255) #red 

thickness=4 lineType=LINE_AA shift = 0 

circle(img, center, radius, color, thickness,lineType, shift) 

rectangle(img, cvPoint(30,30), cvPoint(150,150), cvScalar(255,0,0), thickness, lineType, shift)

3. display it

imdisplay(img, "Drawing")
closeWindows(0,27,"")